1. Field of the Invention
This invention relates to a device suitable for correcting spinal deformities and for use in treatments for correcting various spinal deformities of congenital or acquired type.
2. Background of the Prior Art
A device of the kind shown in FIG. 7 is generally used in procedures to correct congenital or acquired spinal deformities due to scoliosis, kyphosis, spinal caries, spondylolisthesis and injury of the spine.
The device 31 per FIG. 7 comprises a distraction rod 37, having a length sufficient to correct the curved or deformed spine to a predetermined shape, and hook members 32 which are attached on the distraction rod 37 to be engaged with the transversal projection or vertebral arch of a patient.
The distraction rod 37 is formed of metal in a substantially linear form, and is knurled on the outer surface to give an irregularly textured portion 38 thereto.
Each hook member 32 includes a main body 32a in a substantially rectangular form with a hook 33 on one side thereof, a retaining groove (or retaining hole) 34 for inserting and retaining the distraction rod 37 within the main body 32a on the side opposite to the hook 33, and a lock bolt 36 for fixing the rod 37 when it is inserted in the hole 34 at a predetermined position.
The device 31 is fixed to a patient by engaging at least two hook members 32, 32 with transversal projections or portions of the vertebral arch of the spine which are exposed by surgery for gradually pulling or stretching the deformed spine to a predetermined shape, and inserting the distraction rod 37 through the holes or grooves 34 of the hooks 32, 32 for maintaining the spine in a corrected state. Fixing bolts 36, 36 are then tightened to support the pulled or stretched spine, and the muscular tunics, the fascia, and the skin of the patient are sutured so that the fixed state of the device may be maintained for a given period. Through-hole 35 is provided to secure insertion and engagement of the hook member 32 at a predetermined location on the spine with hookholders.
The prior art device mentioned above is an improvement made on a spinal deformity correction device which was developed by Paul R. Harrington in Houston Texas, USA in 1962, and has been widely used.
The known spinal deformity correction device with the above-mentioned structure has a knurled surface on the outer periphery of the distraction rod so as to enable secure engagement of the hook member when fixing bolts are inserted. The knurled rod, on the other hand, may have an adverse effect on the human body and may lower the rigidity of the whole rod. The knurled surface moreover, prevents hook members from smoothly sliding on the rod due to high frictional resistance.
As this device has the hook members fixed on the rod by tightening bolts, the operation of tightening/loosening the bolts is quite cumbersome.
The prior art device is inconvenient to use in that the knurled surface increases resistance, causes extra difficulties, and prolongs the recovery time.
There is, therefore, a need for a more effective and advantageous spinal deformity correction device.